AlNiCo Magnets

AlNiCo magnets have been mass-produced for over 50 years. Their name comes from the alloy composition of which they are manufactured. They contain: 7-10% Al, 13-16% Ni, 20-40% Co, being Fe the remaining constituent. Besides, Alnico magnet contains such additions like Cu (3-5%), Ti (1-8%) and Nb, or Ta. For their production employed can be either metallurgical methods (casting), or powder metallurgy (sintering). At present, most often, they are manufactured as anisotropic magnets.

AlNiCo Magnets

From among all types of magnets, alnico magnets are characteristic of the highest temperature stability of magnetic parameters, very high Curie Tc temperature, as well as maximum working temperature Tmax, related to to the last one. They are also marked out by the highest corrosion resistance. Maximum values of their energy density (BH)max are a bit higher or similar to those of (BH)max for ferrite magnets, while values of their remanence Br are similar to those of Sm-Co sintered magnets. Their reverse permeability is 2,7 times bigger than that of other magnets. However, small values of coercive force jHc make impossible to apply alnico magnets in the presence of strong demagnetizing fields, which limits their applications. Moreover, their low coercive force affects determination of the working point of alnico magnets. Low (flat) alnico magnets, immediately after taken out of the field magnet get considerably demagnetized, and their working point is determined far less than the value of remanence of magnetic flux density. They suffer demagnetization also when have been wrapped or hit, and that is why, in practice, applied are mostly high alnico magnets, that are more resistant to such effects, or they are installed in magnetic circuits and then magnetized, which makes possible determination of their working point close to the remanence Br value.

Alnico magnets predominate over other types of magnets thanks to their temperature stability of magnetic parameters, maximum working temperature Tmax and corrosion resistance.

First of all, they are installed in measuring instruments, control devices, various converters and sensors, motors and generators, and many other appliances (systems), that require stable magnetic field in relation to temperature, and when there is enough space to find room for magnets.

Magnetic and physical properties typical for cast alnico magnets:

Symbol of
material

Remanence
(Br)

Coercive force
(jHc)
Energy
density (BH)max
Density Curie
point
Max.
working
temp.
 
Gs Oe kJ/m3 MGsOe g/cm3 oC oC
LN9 Alnico3   6800   380  9,0 1,13 6,9 810 450

iso-
trope

LN10   6000   500 10,0 1,20 6,9 810 450
LNG12 Alnico2   7200   500 12,4 1,55 7,0 810 450
LNG13   7000   600 13,0 1,60 7,0 810 450
LNG34 Alnico5 12000   600 34,0 4,30 7,3 860 525

aniso-
trope

LNG37 12000   600 37,0 4,65 7,3 860 525
LNG40 12500   600 40,0 5,00 7,3 860 525
LNG44 12500   650 44,0 5,50 7,3 860 525
LNG52 Alnico5DG 13000   700 52,0 6,50 7,3 860 525
LNGT28

Alnico6

10000   720 28,0 3,50 7,3 860 525
LNGT36J Alnico8HC   7000 1750 36,0 4,50 7,3 860 550
LNGT32 Alnico8   8000 1250 32,0 4,00 7,3 860 550
LNGT40   8000 1350 40,0 5,00 7,3 860 550
LNGT60 Alnico9   9000 1380 60,0 7,50 7,3 860 550
LNGT72 10500 1400 72,0 9,00 7,3 860 550


Magnetic and physical properties typical for sintered alnico magnets:

Symbol of
materials
Remanence  (Br) Coercive
force (bHc)
Coercive
force (jHc)
Energy
density (BH)max
Density

Curie
point

 
[Gs]

[Oe]

[Oe]

[MGsOe] [g/cm3] [oC]
FLN8   5200   500   540 1,00-1,25 6,80 760
isotrope
FLNG12   7000   500   540 1,50-1,75 7,00 810
FLNGT14   5700   950   980 1,75-2,00 7,10 850
FLNGT18   5600 1100 1130 2,25-2,75 7,20 850
FLNG28 10500   580   590 3,50-4,15 7,20 850


aniso-
trope

FLNG34 11000   630   640 4,30-4,80 7,20 890
FLNGT28 10000   700   710 3,50-3,80 7,20 850
FLNGT31   7800 1300 1330 3,90-4,50 7,20 850
FLNG33J   6500 1700 1880 4,15-4,50 7,20 850
FLNGT38   8000 1550 1580 4,75-5,30 7,20 850
FLNGT42   8800 1500 1530 5,30-6,00 7,25 850